This application claims the priority of German Patent Application No. 197 45 651.0, filed Oct. 16, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an impact damper for a motor vehicle with an impact plate on which an impact force acts, and an elastically deformable part adjoining the impact plate in an impact direction, with energy absorbed in a collision by the elastic deformation of said elastically deformable part.
An impact damper in the front of a motor vehicle is known from U.S. Pat. No. 3,789,948, said damper having an elastically deformable part with a spring located behind an impact plate on the front bumper, with energy absorbed in a vehicle collision as a result of the deformation of this spring. Depending on the vehicle speed, the impact damper is adjusted for the impact to be softer or harder by a change in spring force. This influence on the spring is accomplished in a costly and cumbersome fashion by an adjustable pressure pump acting on a hydraulic piston.
German Patent Document DE 196 33 110 A1 describes an impact damper for a motor vehicle that has deformation elements with different degrees of stiffness that are plastically deformable in various impact speed ranges to absorb impact energy. The less rigid deformation element is permanently attached in a vehicle zone that receives impact energy, while the more rigid deformation element is moved with respect to the less rigid deformation element as a function of the vehicle speed. During its stress under impact, the impact damper can act to absorb energy only by plastic deformation, so that repair of the impact damper is always necessary. The change in damping behavior can be achieved only through a translational or pivoting movement of the more rigid deformation element by means of a drive, which must then also be able to withstand the stress, making this impact damper costly as well.
A bumper system for motor vehicles follows from German Patent Document DE 41 21 497 C2 that comprises an impact absorber with an impact-damping piston and an impact-damping cylinder. By determining the relative speed between the impact-damping piston and the impact-damping cylinder, a locking mechanism can be activated that can prevent further displacement of the impact-damping piston, whereupon plastic deformation of the impact damper begins to absorb impact energy. Impacts against the bumpers of the motor vehicle are absorbed, with the bumper yielding and the impact-damping piston being pushed into the impact-damping cylinder, so that the bumper likewise no longer returns to its initial position and a visit to a garage is necessary. A considerable structural length is also required for accommodating the piston/cylinder system.
A goal of the invention consists in designing an impact damper of the type discussed above, which can be made economically and so that it can adapt its deformation resistance to the load in a vehicle collision.
This goal is achieved by providing such an impact damper, wherein at least one part can be connected to the elastically deformable part, said plastically deformable being capable of being impacted by the impact plate and absorbing energy plastically in a vehicle collision.
An impact damper for a motor vehicle that has an elastically deformable part that follows an impact plate in the impact direction can absorb impact energy by deformation of this part in the event of a gentle impact of the vehicle, whereupon the elastic part resumes its original shape. For example, a displaced bumper, which acts on the impact damper under the influence of impact force will therefore then be returned to its original position, so that no repairs to the vehicle will be needed.
In order to increase energy absorption in the impact damper for a powerful vehicle collision, a plastically deformable part that can be impacted by the impact plate and is plastically deformable in a vehicle collision can be connected with this elastically deformable part, said part then being able to absorb impact energy additionally and in a greater amount.
The part that is deformable elastically and the part that is deformable plastically in an energy-absorbing fashion can be located to operate in parallel vertically, so that the impact damper, despite considerable absorption ability, need have only a relatively limited height. The least space for installation is then required when one deformable part is made tubular and surrounds the other deformable part with an approximately parallel or even coaxial lengthwise axis.
A coil spring or a plastic damper can be used economically as the elastic part, while the plastically deformable part can simply be formed by a tube.
The plastically deformable part can be connected to the elastically deformable part in simple fashion by a locking part moving into the displacement path of the plastically deformable part that is displaceable by the impact of the impact plate, with the locking part initiating the deformation of the plastically deformable part.
This displaceable locking part can be accommodated integrated into a vehicle-integral support for the elastically deformable part, so that the impact damper requires only limited space as a result.
The two switching positions of the impact damper--an elastic reaction for example to a bump when parking or elastic and plastic reaction in a stronger vehicle collision--can be controlled on the basis of a measured value detected before or during the collision.
In addition, it is also contemplated to certain preferred embodiments of the invention to connect a plurality of cooperating plastically deformable parts in order thus to achieve an especially high degree of energy absorption of the impact damper in the event of a vehicle collision.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.